The present invention relates to dental implants for tooth replacements such as crowns, bridges and dentures in the fields of dentistry, oral surgery and orthodontics and, more particularly, to a mounting system for selected directional support of a dental replacement.
A variety of dental replacement mounting arrangements and methods are known. One commonly used arrangement includes a dental implant in the form of a pin, screw, plate or solid or perforated cone which functions as an artificial dental root, a transmucosal member made of tissue compatible material which extends across the gingival tissue and is either integral with or affixed to the implant to provide a mounting base for an abutment for a dental prosthetic structure. All parts of these arrangements are provided with and interconnected by way of central axis boreholes and cooperating fasteners engageable therewith. Arrangements of this type are disclosed in U.S. Pat. No. 3,435,526 by Brancato, U.S. Pat. No. 4,016,651 by Kawahara et al., U.S. Pat. No. 4,178,686 by Riess et al., and U.S. Pat. No. 4,713,006 by Hakametsuka et al.
Attachment bases or implants for dental replacements are inserted or screwed into the jaw bone. However, since jaw bones are often rather narrow and are inclined in vertical direction and the attachment base must, for technical reasons, be well centred in the jaw bone, the longitudinal direction of the attachment base may not be in alignment with the longitudinal direction of adjacent teeth or abutments, because of the constructional restraints of central axis boreholes. This is a problem, since the teeth of the prosthetic structure should ideally align with the attachment base for maximum strength of the whole arrangement. The result is either a weak and unsatisfactory connection between the implant and the jaw bone or a misaligned prosthetic structure. Thus, a dental replacement arrangement is desired which would provide for compensation of a misalignment between the longitudinal direction of the implant and the longitudinal direction of adjacent teeth or abutments thereby ensuring that the prothetic structure is aligned with the attachment base.
Bostrom in U.S. Pat. No. 3,732,621 describes an implantable fixture for a dental prosthetic structure which fixture includes a first part for embedding into the jaw bone and a second part which serves as an attachment base for the prosthetic structure and passes through the weak tissue covering the bone tissue. The first and second parts are interconnected by way of a sealed ball and socket joint which can be locked in a desired angle or position. Thus, a misalignment of the implant with respect to the surrounding teeth can be compensated without misalignment of either the implant in the jaw bone or the prosthetic structure on the attachment base. However, the ball and socket joint may become unlocked when the prosthetic structure is subjected to biting stress or when the dental surgeon has to screw on the prosthetic structure. This can lead to misalignment of the attachment base. The misalignment can then only be corrected by removal of the prosthetic structure and resetting of the joint, which can be a serious problem if the prosthetic structure has already been permanently cemented onto the attachment base leaving the joint locking screw unaccessible.
Another attempt at solving the problem of angulation are angled abutments which are directly screwed into the implant and are commercially available, for example from CORE-VENT CORPORATION (Encino, Calif.). Although angled abutments can be used to compensate for angulation, they are unsuited for applications where lateral working space is restricted such as in single tooth replacement. The diameter of the circle, described by the abutment tip during screwing into the implant is frequently larger than the distance between adjacent teeth, making it impossible to use the angled abutment or forcing the dentist to use an abutment which does not fully compensate implant angulation. Thus, a tooth replacement mounting system is desired which fully compensates any implant angulation present and can be used in confined spaces.